What is the urgency to develop an HIV vaccine?
With no cure for HIV/AIDS and behavioural interventions failing to stop the spread of the HIV infection, a preventive vaccine is considered the best approach to end the spread of the disease. HIV is estimated to infect over 7,000 people around the world each day. The work on finding this vaccine has been on for more than 25 years since the first cases were detected. However, the epidemic rages on as scores of research projects and studies on HIV vaccines have been shut down because the line of vaccine being studied did not work.

What are the biggest hurdles to developing a vaccine for HIV?
The researchers have to identify the most effective immune response that will provide long–term protection and then decide whether it would be better to target specific immune responses or a combination of different responses. Besides, there are so many different types of HIV viruses with subtle genetic differences that need different treatment approaches to tackle them. For any vaccine to be effective, it will have to offer long term protection to a broad spectrum of HIV viruses. The virus also mutates continuously and evolves. So, even if a person is vaccinated against an earlier variant, a mutant variety could still lead to infection. Moreover, HIV vaccine research, like any other drug or vaccine research, is very expensive. Two large trials in 2003 and 2007 failed, leaving researchers wondering if there could ever be an effective vaccine. Since the 1980s, the National Institutes of Health in the US are said to have spent $3.4 billion on HIV vaccine research alone. The search for this elusive vaccine received a boost when the Bill and Melinda Gates foundation gave a quarter of a billion dollars towards this research to 19 countries. The appearance of resistant strains of HIV virus, strains resistant to the modes of treatment currently available, is another matter of great concern.

What is the latest breakthrough in HIV vaccine research?
A latest vaccine, a combination of two different genetically engineered vaccines that did not individually work in human beings, is said to be the first to show at least partial success. It underwent Phase–III trial in Thailand involving over 16,000 uninfected volunteers. The international Data and Safety Monitoring team reported that there were no safety concerns as the vaccine under study did not cause any HIV as it was not made from and did not contain the entire virus, either live or killed. Of those who got placebos, 74 became infected, while only 51 of those who got the vaccines did. While this might not seem very encouraging, the team studying the vaccine said it was statistically significant and meant the vaccine was 31.2% effective, way better than the results with many others under study. Incidentally, male circumcision is shown to reduce the risk of infection by double that.

How far are we now from an effective HIV vaccine?
Though there is much cheer about the success of the trial, it is a long road ahead with some estimating that it could take as long as another decade for an effective vaccine. Following the successful trial, the next task would be to identify how the vaccine worked to protect the people. It is also worrying that among those infected, the levels of virus in the blood were the same whether they had been vaccinated or not. The results of the trial have to be published and peer reviewed. It also has to be determined how many strains of HIV the vaccine protects against. So, a universal vaccine that works might be quite a long way off.

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